Fig. 1.

Core-shell structure of the Au₁₀₂(p-MBA)₄₄ cluster. (a and b) Space-filling (a) and ball-and-stick (b) representations of the Au₁₀₂(p-MBA)₄₄ nanoparticle. Au, orange; S, yellow; C, gray; O, red; H, white. (c and d) Two views of the 40-atom surface of the Au₇₉ core, together with the passivating Au₂₃(p-MBA)₄₄ mantle. The cationic Au atoms in the mantle are depicted by the smaller orange spheres. The “structure defects” at the core–mantle interface [two Au atoms with two Au–S bonds, and a long RS–(AuSR)₂ unit] are highlighted by the ellipse. (e) Close-up of the protecting RS–(AuSR)_x unit with x = 1 or 2. (f and g) Two views of the Au₇₉ core, which has a symmetry of D_5h (within 0.4-Å tolerance).